Vertical CFA
Hi Valley,i want your help.
Jeff has send some boards to me,including the vertical CFA IPS.
1)As i want to run this at +\-50V it is necessary to trim some resistors.
Can you help me?
2)Where i can find the final schematic as built?
Hi Valley,i want your help.
Jeff has send some boards to me,including the vertical CFA IPS.
1)As i want to run this at +\-50V it is necessary to trim some resistors.
Can you help me?
2)Where i can find the final schematic as built?
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I think Valery did all his testing on a 50V supply. I ran mine on both 50V and 64V with no changes.
Hi Thimios!
Just in case - here is the "as built" schematic.
You've got the 1-st version PCBs, so:
- don't install C16, C17 (47pF) - they were in parallel with R17, R18 - not on scematic any more, but you will see them on the silk. Leave them blank.
- add two 22pF caps - C18, C19 - they are not on PCB, but on the schematic now. Place them under the board - see the picture. New version of the PCBs already incorporates these changes.
Tested mine with +/-52V - no problem. Just in case - measure the voltage across D1, D2 zeners. If you see less than 15V - change R8, R28, R9, R29 to 4.7k - will be perfect for +/-50V or even a bit less. All the rest is automatic.
Cheers,
Valery
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Ok thanks Vallery!
Just another question🙂
I haven't any 5k6 2w for use as feedback resistor.
Is it a big difference using 6k8 2w?
edit the schematic at servo inp.
Just another question🙂
I haven't any 5k6 2w for use as feedback resistor.
Is it a big difference using 6k8 2w?
edit the schematic at servo inp.
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Ah - sorry, Diptrace just moved the line at some point - you're right.
6k8 2W - ok, but in this case use 130R for R5, R6 - this will keep the gain close to 29db.
vertical cfa
Here is mine vertical.
Connecting this to a slewmaster test board, it is singing.
Unfortunately is unstable.🙁
Trying to increase the idle current to something more than 2mV this rise quickly to 350mV.
I haven't any 4u7 for servo so i use 6u8 in this position.
I see that VAS current is 10mA.
Vallery is this ok?
Here is mine vertical.
Connecting this to a slewmaster test board, it is singing.
Unfortunately is unstable.🙁
Trying to increase the idle current to something more than 2mV this rise quickly to 350mV.
I haven't any 4u7 for servo so i use 6u8 in this position.
I see that VAS current is 10mA.
Vallery is this ok?
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You have to lower the vas output to use it with the Slewmaster. I think Valery told which resistors to change somewhere in this thread. When I get to my computer I will try to find it.
R19, R20.
560R less than 8mA. Even better for Slewmaster - use 470R there.
680R gives you 10mA of VAS current.
The less the value - the less the VAS current 😉
All the rest looks good
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1k5 installed parallel to 680R . VAS current is 5mA now,but the problem is still here .
Up to 5mV on R22 emitter resistor(22,7mA idle current) it seems stable but when this a little rise rapidly comes to unstable.
A frequency counter at zobel resistor show 6.7MHz
Up to 5mV on R22 emitter resistor(22,7mA idle current) it seems stable but when this a little rise rapidly comes to unstable.
A frequency counter at zobel resistor show 6.7MHz
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2sc5200,a1943
Today i try again many of the ostriper,cfa without any problem
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Can you please drop the schematic here? Looks like a local OPS oscillation to me.
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